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Oscillating December Temperatures and 2017 Climate Review

December 22, 2017

Oscillating December Temperatures and 2017 Climate Review:

Through the first three weeks of this month most climate observers have reported average December temperatures that range from 3 to 7 degrees warmer than normal. With the projected colder than normal weather dominating the Christmas to New Year’s Day time period, it appears that by the end of the month most climate stations will find that December mean temperatures have balanced out close to normal. Minnesota has reported the coldest temperature in the nation only twice so far this month, but is likely to see this frequency increase over the last ten days of the month. This oscillating temperature pattern is what balanced out the month of November as well, expect the first half of the month was exceptionally cold and the second half of the month exceptionally warm.

January may continue this oscillating pattern as it starts out colder than normal, then moderates mid-month and may even warm to above normal during the second half of the month.

Looking Back at 2017:

With most of the year in the rear view mirror now perhaps a look backward would be appropriate. The year 2017 is likely to end up among the ten warmest in state history. Both Granite Falls and Browns Valley recorded temperatures of 100 degrees F (July 17). Overall, only the months of May and August were colder than normal. Within the statewide climate network over 600 new daily maximum temperature records were set, while over 600 new daily warm minimum temperature records were set during the year. Most of these records were in the months of January, February, and September. Relatively few new low temperature records were set during the year. Coldest temperatures reported during the year were in mid-January when Blackduck, Celina, Embarrass, and Cotton reported lows of -40 degrees F or colder. A reading of -46°F at Cotton (St Louis County) on January 14th was the coldest reading of the year.

Most climate stations reported a wetter than normal year in 2017, but not anything close to a record value. Geographically the northwestern and north-central portions of the state reported less than normal precipitation for the year, while the rest of the state, especially northeastern and southeastern counties were well above normal. Among the long term climate stations in the state only Minnesota City (Winona County) reported a new record wet year with a precipitation total over 49 inches. A few climate stations in northwestern Minnesota reported less than 20 inches for the year. Within the state climate network over 500 new daily precipitation records were set, with the most occurring in the month of October, so wet that it delayed the corn harvest. The heaviest thunderstorm of the year occurred on August 16 when several observers reported over 5 inches of rain, and Redwood Falls reported 8.12 inches, a new statewide record for the date.

Ice dominated the weather headlines during January and February, especially in the southern half of the state where there were hundreds of auto accidents as well as pedestrian injuries reported. During these months at least six days brought rain, instead of snow, but then the rain froze overnight, leaving a coating of ice for the morning commute.

According to Warning Coordination Meteorologist Todd Krause of the National Weather Service, Minnesota reported 61 tornadoes this year, a larger than normal number. This is preliminary as the final report for 2017 is not finished.

Despite a rainy first few days, the weather during the State Fair (Aug 24 to Sep 4) was very favorable with comfortable temperatures, low humidity, and light winds. As a result a new record attendance was set with 1,997,320 people spending time there.

More on the weather headlines of the year will be in next weeks WeatherTalk Blog.

Weekly Weather Potpourri:

Much of the state received snowfall on December 21 though a section in the middle of Minnesota only received a dusting. In the northern third of the state reports ranged from just an inch to over 8 inches in some parts of Hubbard, Cook, and Carlton Counties, while 2 to 5 inches of snow fell across some southern counties. Pipestone reported 5.3 inches.

Jake Crouch of NOAA offers an interesting glimpse at climate trends across the nation in a blog post this week. Minnesota happens to show some of the strongest upward trends in both temperature and precipitation among all the states in the USA.

In the Western Pacific Ocean Tropical Storm Tembin will bring large waves, strong winds, and heavy rains to portions of Vietnam and Thailand over the coming Christmas holiday. Winds are expected to 70 mph or greater and sea waves may exceed 20 feet with this storm.

MPR listener question:

We just moved to the Twin Cities from Florida this autumn and look forward to having our first White Christmas. But what is with these subzero overnight temperature forecasts between Christmas and New Years Eve? Is that the normal around here?"

Answer:

For the Twin Cities we usually get at least one subzero temperature reading between Christmas and New Year’s Day 75 percent of the time (back to 1872). It has been as cold as -39°F on Christmas Day (1879) and as cold as -30°F on New Years Day (1974). But since 2002 only 4 years have brought overnight subzero temperatures to the Twin Cities between Christmas Day and New Years Day, and in 2011 the day after Christmas reached a high of 52°F. So we have certainly been experiencing a trend toward milder temperatures during the holiday season. This year will obviously been different, as the forecast calls for several nights to drop below zero.

Twin Cities Almanac for December 22nd:

The average MSP high temperature for this date is 25 degrees F (plus or minus 13 degrees F standard deviation), while the average low is 10 degrees F (plus or minus 13 degrees F standard deviation).

Average dew point for December 22nd is 13°F; the maximum dew point on this date is 44°F in 1941; and the minimum dew point on this date is -32°F in 1983.

All-time state records for December 22nd:

The all-time state high temperature for today's date is 62 degrees F at Two Harbors (Lake County) in 1899; the all-time state low for today's date is -44 degrees F at Baudette (Lake of the Woods County) in 1963. The all-time state record precipitation for this date is 1.30 inches at Glencoe (McLeod County) in 1920. Record snowfall is 16.0 inches at Artichoke Lake (Big Stone County) in1968.

Word of the Week: Snowcreep

This word does not refer to the guy who just put a snowball down the back of your neck, nor is it the snowplow driver who just cleared the alley by pushing all the snow onto your driveway. It is a term used to describe the slow, continuous downhill movement of a snowfield or mass of snow on a slope. Most often associated with mountainous areas, this feature can also be observed on less topographic terrain as well, such as the ridges of the Lake Superior shoreline, or the Mississippi River Valley in southeastern Minnesota.

Past Weather Features:

Very warm weather occurred on December 22, 1877. Temperatures were in the 50s F across southern Minnesota and even the mid 40s F in Duluth. Later in the day rain fell across most of the state, making for a muddy Christmas season.

Another very warm December 22nd occurred in 1899 as over 25 climate stations reported daytime highs ranging from 45 to 55 degrees F. The temperature reached 62 degrees F at Two Harbors, an unusual day indeed.

The coldest December 22nd in state history occurred in 1963 when over a dozen climate stations reported morning lows of -30°F or colder. The afternoon high temperature at Hallock (Kittson County) in the Red River Valley only reached -10°F.

A strong winter storm brought heavy snow and blizzard conditions to the state over December 21-22, 1968. Many areas of the state received 8 to 16 inches of snow, and 40 mph winds created some huge drifts and road closures. Over 40 climate observers reported new snowfall records on the 22nd.

The week of December 17-24, 1983 was one of the coldest in Minnesota history. Many climate stations reported average weekly temperatures that were 30 to 35 degrees F colder than normal. The average temperature for the week in the Twin Cities was -14°F. Over 35 climate stations reported minimum temperatures of -40°F or colder, while Tower and Mora reported -52°F. Many wind chill readings were -60 degrees F or colder.

Outlook:

Generally dry over the Christmas weekend, but with temperatures well below normal. Monday and Tuesday will be the coldest days next week with many daytime high temperatures remaining below zero F. There will be some moderation in temperature towards the end of next week, but remaining colder than normal. Slight chance for snow on Wednesday and Thursday.